Caplin's con man heaps scorn and embarrassment on the Blairs

Peter Foster, the Australian con man who made a brief appearance in the lives of Tony and Cherie Blair, has surfaced again with a string of extraordinary claims about life inside Downing Street.

Mr Foster, who has numerous criminal convictions for fraud, has launched an energetic new campaign of self-publicity, apparently in an attempt to boost his unpublished memoirs.

In a lengthy interview with The Independent on Sunday, Mr Foster claims that the influence his former girlfriend, Carole Caplin, wields over the Prime Minister is so great that "she gives him advice on strategies for handling Gordon Brown, and dresses him down to his boxer shorts".

Ms Caplin's ties with Mrs Blair became a source of friction within Downing Street, hastening the departure of Mrs Blair's media adviser, Fiona Millar, the partner of Alastair Campbell.

In December 2002, Mrs Blair had to make a tearful apology on television after it was revealed that she had accepted Mr Foster's help in buying two apartments in Bristol, where her oldest son was starting university.

Ms Caplin, Cherie Blair's former lifestyle adviser, whose relationship with Mr Foster ended over a year ago, said: "This is just a new way for Peter to get attention. He is just a fantasist, and these absurd stories shouldn't be given any credibility."

Mr Foster was also interviewed in yesterday's Sydney Sun-Herald in Australia. He made lurid and scurrilous claims, and boasted that his memoirs contained a "weapon of mass destruction" aimed at Downing Street.

In a statement last night Downing Street said: "We have absolutely no intention of taking these claims seriously, and neither should anyone else."